Coded continuous inductive train control system



March 16, 1943'.

c. s; BUSHNELL GODED CONTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM FiledApril 1, 1941 2 Sheets-Sheet l Z 22. i 23 2 I2. 2 2.. 2 .1.

tti? neH,

'lNVENTOR BY C.S.%sh H IS ATTQNEY.

March 16, 1943. c. s. BUSHNELL CODED CONTINUOUS INDUCTIVE TRAIN CONTROLSYSTEM Filed April 1, 1941 2 Sheets-Sheet 2 INVENTOR BY 05; Bushnel l,

H IS ATTORNEY.

Patented Mar. 16, 1943 UNITED STATES PATENT OFFICE CODED" CONTINUOUSINDUCTIVE TRAIN CONTROL SYSTEM Charles S. Bushnell, Rochester, N'. Y.,assignor'to General Railway Signal Company, Rochester,

' Claims.

The present invention relates ingeneralto train control systems of thecoded continuous inductive type, and has more particular reference tocar carried decoding apparatus for such systems.

More specifically; the invention relates to a hydraulic or fluidpressure device, responsive to coded trackway energy to decode suchtrackway energy and control car carried signals and the like.

In one form of the invention the decoding and control means as well asacknowledging means is constituted entirely by fluid pressure responsivemeans.

In a second form of the invention, the primary decoding means ispressure responsive, but the signal control means, acknowledging means,etc., include electro-magnetic means arranged to properly carry out thedesired functions.

Further objects, purposes, and characteristic features of the presentinvention will appear as the description progresses, reference beingmade to the accompanying drawings showing in a purely diagrammaticmanner and in no Way whatsoever in a limiting sense, two forms which theinvention can assume In the drawings:

Fig. 1 is a wholly schematic showing of one form of the invention.

Fig. 2 isa wholly schematic showing of a second form of the invention.

Referring now to the drawings, and first to Fig. 1, there is here showntrackway apparatus in eneral similar to the disclosure in the I-Iailespatent, No, 1,910,794, granted May 23, 1933; and likewise in theReiohard application Ser. No. 253,320, filed January 28, 1939.

The drawings show a stretch of single track constituted bytrack rails I,with usual insulating joints 2, to form isolated track sections. At theentrance end of each section, travel being in the direction of arrow 3,is connected a track relay TR, while across the exit end isconnected atrack transformer T having a. secondary winding. in series with anadjustable resistance 4, an adjustable inductance 5,. and a trackbattery TB. The primary winding of track transformer T is connected to asource of alternating current, here shown as of a frequency of 100cycles per second, by way of contacts. of the track relay, and contactsof a line relay LR which. is controlled. in a usual manner through aWire 6, by thetrack relay for. the block next in advance.

Thus, coded energy formed by acode motor CM, which in turn iscontrolled. byacodemotor-control relay CMCR, controlled through a wire'I' by theztrackrelay next. to the-rear, is placed'across the exit endof eachblock when the block is occupied. by a vehicle. The code isselected as is obvious from the drawings, and from the. dis closuresabove referred to, in accordance withtraific conditions in advance. Thecontrol energy is coded at three different rates, 180, and '75 perminute. In accordance with usual practice the block immediately to therear of an occupied blockv is supplied with. code at the rate of '75impulses per minute, the block next to the rear thereof by l20rate code,and the block next tov the rear thereof and all blocks further to therear at rate code. An occupied block has its code shunted out by thewheels and axles of the occupying vehicle whereby a second vehicleentering such occupied block receives no codeenergy.

As shown: in the drawings, the forward block is occupied by a vehicle,indicated by the'wheels and axle 8, and to the rear of thisvehicle, andin the same block a second vehicle is indicated by the wheels and axle8? and receiver coils R, connected in the usual. manner to a car carriedreceiving circuit tuned for 100 cycle current. This circuit includes anampli-filter I3, the output side of which-is connected to a codingprimary relay CPR whereby to cause the relay to follow the code andclose its contact finger I4 on its front point for every impulse of codecurrent.

The car carried apparatus includes a code following repeater relay CFRPwhichcanbe. of any usual or desired construction. It is here shown as ausual tractivetype. relay having a winding I5, a pivoted armature. I 6biased by a spring or the like IT to retracted. position. This codefollowing repeating relay is connected so as to be energized wheneverrelay CFR picks up. whereby to cause its armature IE to oscillate atthev rate of theexisting code.

Mechanically connected to the code following repeater relay is a pumpwhich can be. of any usual or desired form, but is here shown as adouble acting pump having a pivoted operating rod IB' connected toopposed diaphragms i9. and 2!), whereby to pump liquid from-a supplytank S through pipe 2| and force thisliquid into a pressure tank Pthrough pipe 22. Theflow of liquid is controlled in a usual manner bycheck valves 23, or thelike.

By means of the system. as described so far, it is clear that liquid ispumped. from chamber S tochamber P at a. rate corresponding to thetrackway codethen in force.

Thev tanks S and Pam separated by av partition 24 having'a restrictedaperture 25 therein, whereby to. interconnect the tanks at a. point.immediately abovethelevel of the liquid 26 whenthe system is at rest;that is, when no code is present in the track rails. A restrictedaperture 2'! connects the upper portion of tank S to atmosphere. Leadingfrom the upper portion of pressure tank P is a pressure pipe 28 which isemployed to control car carried apparatus as will appear below.

To briefly summariz the operation of the system so far described, itshould be noted that, in accordance with the rate of the code beingreceived, pump P operates to transfer fluid from tank S to tank P andthat immediately upon the pumping being initiated the level of liquid intank P rises above aperture 25. Thereupon liquid flows back from tank Pto tank S at a rate which is slower than the slowest rate of supply tothe tank P at the beginning of the opera- I tion. However, as the liquidlevel rises in tank P and the air in the closed space above the liquidlevel becomes further and further compressed, the rate of flow back fromtank P to tank S increases until a balance is finally reached where thelevel remains constant in the tank P because the volume of flow and theoutflow is the same rate. This level, and the corresponding pressureabove the surface of the liquid in tank P will be difierent for eachdifferent rate of code since the pump supplies a given volume with eachstroke regardless of the back pressure. Accordingly, a pressure existsin pipe 28 leading from the upper end of tank P, which corresponds tothe code rate of energy being received and which is higher or lowerdependent upon whether the code rate be higher or lower.

The liquid employed in the tanks S and P can be of any suitablecharacter, such as water or if the temperature conditions are unsuited,such as oil, or the like.

When the system is at rest, the surfaces of the liquid in the two tanksS and P are under atmospheric pressure, and the spaces above the liquidsurfaces in the two tanks are unconfined, and hence the pressure in pipe28 is substantially unchanged by changes in ambient temperature. Shouldthe ambient temperature change during operation of the pump, under suchconditions of course, the space above the liquid surface in pressuretank P, is confined, the air therein will either increase or decreaseits pressure, thus to cause an increased or decreased flow of liquidback into tank S through aperture to thus adjust the pressure.Accordingly, while the liquid level attained at a given code rate maydiffer under different temperature conditions, the resulting pressure inpipe 28 will be substantially constant at any given code rate,regardless of ambient temperature changes.

It is of course desirable that the aperture 25 remain open duringoperation of the system and not become clogged up to any substantialextent, and with proper inspection, and with wide enough margins betweenthe different indications, as will appear from the following descriptionas being entirely practical, there is small chance for any failure ofthe system on this count.

Connected to the pressure pipe 28 leadin fro the upper portion of tank Pis a header tube 28 to which is connected a series of U-tubes,comprising tubes A, B, C and D. Each tube, such as tube A, has one endhermetically connected to the header 28 and th other end extendin abovethe header and open to atmosphere as at 29. Within each U-tube is aquantity of liquid which is of a character to be electricallyconductive, and one liquid which is contemplated as being employed ismercury. Any other suitable or desirable liquid or mixture can equallywell be employed.

Carried on the car is a cab signal IS which in the present instance isshown as a light signal employing four lamps IG, IY/G, IY and IR whichare colored respectively, green, yellow over green, yellow, and red.These lights indicate respectively, proceed, proceed prepared to passnext signal at reduced speed, proceed prepared to stop at the nextsignal, and stop.

Controlling signal IS are the two U-tubes A and B, each having a seriesof contacts with a contact in each series, corresponding to a signallamp. The contacts in the tube A are in the leg subjected to atmosphericpressure and are arranged downwardly from G to R, while those in tube Bare positioned in the pressure subjected short leg, and are arrangedreversely to that in tube A, that is, from R downwardly to G Each lampis controlled through a circuit which includes a corresponding contactin each of the two tubes A and B. For example, the system, as shown, isat rest since the receiver R is in an occupied block whereby no code isbeing received and the pump IP is at rest. Under these conditions,atmospheric pressure exists in both legs of the U-tubes whereby theliquid 30, such as mercury is at the same elevation in the two legs ofthe tubes and is of a quantity to be just above the lowest contact intube A, namely, contact R, and just above the highest contact in tube B.namely, R Thus, the cab signal shows a red indication since the lamp IRof th signal is energlZed through a circuit which includes the mercury30 in tube A, contact R, wire 3I, lamp IR, wire 32, contact R andmercury 30 in tube B.

If we assume that vehicle 8 leaves the block occupied by the vehiclehaving the receiver R, energy coded at the rate of 75 impulses perminute is received by the vehicle in question, whereby to pump liquidfrom tank S into tank P at a given volume rate per minute, to therebyraise the pressure in header 28 to a given figure. This causes theconducting liquid in U-tubes A and B to rise in the atmospheric leg andto lower in the pressure leg whereby to break the energizing circuit forlamp IR at contact R and make a like energizing circuit for lamp IY atcontact Y.

It can be noted that, as the existing circuit is broken in tube B, thenew circuit is made in tube A and shouldthe contacts be so positioned asto cause a lapse of time between these two occurrences, a dark signalwould meantime result. If on the other hand, the contacts are soarranged as to make the new circuit, before the existing circuit bebroken, there would be a period of time during this overlap when. thesignal would display two different indications. It is contemplated thatthe contacts will be so positioned with respect to each other that theexisting circuit will be broken at substantially the same instant thatthe new'circuit ismade or possibly that there be a short lapse of timeof a few seconds during which the signal will be dark.

In a manner similar to that described above, the various aspects of thecab signal are displayed upon the receipt of the various rates of codedenergy. In order that a signal shall not fail during the brief period oftime when the vehicle may be passed over a crossover, or the like, andin order that a signal shall not change to a new aspect until after itis assured that this is intended as checked by several cycles of the newcode occurring, it is necessary that the control means be somewhat slowacting. While in the usual'relay control of vehicle apparatus, slowacting characteristics are imparted by repeater relays, and the like, inthe present systemxthis is quite unnecessary since the pressure devicesemployed are inherently sufiiciently slow acting as to produce thisdesired effect.

The tubes C and D are connected to the header as are tubes A and B, andcontain a conducting liquid such as mercury. The tube C has a pluralityof contacts therein, positioned at different levels and correspondingwith the signal aspects and designated in a descending order, as 9,11/9, 1/ and 1'. Like corresponding contacts in tube D are arranged inthe reverse order as regards their level, namely, in an ascending order,designated as T y/g y and g As with tubes A and B, the contacts in thesetubes C and D are arranged respectively in the atmospheric leg and inthe pressure leg.

Tube D is equipped with a check valve 3| of the ball type, which seatsdownwardly, and with a bi-pass tube 32 around the check valve with ashut-off valve 33 of the gate type for preventing flow of liquid fromone side of this valve to the other, or, in other words, for normallymaking the bi-pass 32 inoperative. The valve 33 constitutes a part of anacknowledging contactor Aclc.C. which can be manually operated by beingpushed in a direction to open valve 33, but which normally is biased tothe valve closing position by suitable means which in the presentinstance can be a spring biased contact finger 34 with a biasing spring34 connected by an obvious circuit to a whistle valve WV, which, whendeenergized, sounds a warning, and which, to be silenced, must bereenergized.

With the system at rest as shown, the two contacts 1" and r complete anenergizing circuit for whistle valve WV to maintain the whistle silent,the circuit including mercury 30 in tube C, contact 7, wire 35, contactr mercury 30 in tube D, wire 35, contact finger 34 and back point, andthe whistle valve WV.

Assume now that trackway conditions change as referred to above, so thatenergy coded at the '75 rate is received. Pressure will build up to a"given value in header 28 whereby to raise the mercury level in theatmospheric leg of tube C and lower it in the pressure leg of tube Dwhereby to make contact with y in tube C and break contact with r intube D. The contacts are so positioned with respect to the conductingliquid that the y contact is made before the r contact is broken,whereby to maintain the whistle valve energized and prevent any warningsignal. It should be noted that this same operation occurs as the codechanges to less and less restrictive codes ultimately to complete anenergizing circuit for the whistle valve which includes the contacts aand 9 In this operation it can be seen the check valve 3| 1 has noeffect in preventing the rise of liquid level in the atmospheric leg oftube D.

Assume now that with the code rate at 180 per minute there is a changeto a more restrictive code rate such as 120 per minute. The pressure inheader 28 decreases whereby to cause the conducting liquid to drop inthe atmospheric leg of tube C so as to break contact with contact 9.Since the contact y/gi is already made, however, unless means wereprovided for preventing it, the whistle valve would remain energized inthe same manner as described above in connection with a change in codefrom more'toless restrictlve. The liquid in atmospheric leg of tube I)cannot drop, however, because of check valve 31 and. the acknowledgingvalve 33 whereby the liquid cannot rise in pressure leg of tube D tomake the 21/0 contact. Thus, upon contact 9 being broken the whistlevalve is deenergized and sounds a warning which continues until theacknowledging contactor is operated to thereby open valve 33 and permitthe liquid level in pressure leg of tube D to rise and find its normallevel under the pressure conditions existing whereby to complete contacty/c' and reenergize the whistle valveand silence it. I

The operation in each of the changes from less to more restrictiveconditions is the same as just described. In each case the whistle valveis sounded to apprise the engineer that conditions have become morerestrictive and that he should be alert, and this is assured, and hisrequirement that he complete the acknowledging act required in order tosilence the signal.

In the acknowledging system of this form of invention, if the contactsare so arranged that upon passing from r to y, for example, the contactr is broken before the contact 3/ is made, the whistle sounds untilcontact 2/ is made. If the contacts are so arranged there is a resultingshort blast 'of the signal device on going to less restrictiveconditions, for apprising the engineer that a change in trafficconditions has occurred, but this blast can be made so short as to notrequire the acknowledging act.

If, however, the contacts are so arranged as to have contact r brokensimultaneously with the making of contact y or even slightly later, thenwhen contact y is made, there is no operation of the whistle on changesto more favorable conditions.

The acknowledging contactor can of course be remotely controlled by anyusual mechanical or electrical means, the essential feature being thatsome act on the part of the engineer is required upon every change tomore restrictive conditions to silence the whistle or remove any otherpenalty, such as a brake penalty, or the like.

The system as thus far described involves'car carried apparatus andemploys but two relays, one of which operates the pump and does not havethe usual relay function of passing electrical energy on to a furtherinstrumentality.

It should be noted that a code following relay CFR is employed but thisrelay is not essential and could be eliminated entirely under certainconditions whereupon the code following repeater relay would have itswindings connected directly to the output side of the ampli-filter.

Referring now to Fig. 2, which shows a modifled form of the presentinvention, there is here shown a pressure tube 21 which corresponds tothe tube 28 of the form of invention shown in 1. In the form ofinvention of Fig. 2, the trackway apparatus and pumping system, togetherwith the supply tank and pressure tank, can be identical with what hasalready been disclosed. Thus, pressure exists in tube 2'! in accordancewith whether any code is in force and with what particular code is inforce. In other words, the pressure in tube 2'8 is atmospheric pressureunder danger conditions or when the system is not cut into service andis above atmospheric to various degrees in accordance with whether thecode isrelatively slow or fast. v

In this form of invention there is a pressure chamber P? which containsair at atmospheric pre'ssureifth'erebe no code present, and at high erpressures as any code present increases in its rate. Associated with thepressure chamber are three code responsive pressure relays 15R, I20R andi8OR all constructed in substantially the same way.

Considering the structure of relay 15R, for example, it is constitutedby a diaphragm 36 subjected to the pressure of the pressure chamber onone side and to that of a biasing spring 31 on the other side. It has astem 38 comiected to the diaphragm and in turn connected to a contactfinger 39 by means of a pin 40, the finger being pivoted at 4|. When thepressure in chamber P is atmospheric the diaphragm assumes the positionshown and the contact finger 39 makes up its back point.

Upon the slow rate code of 15 being received the pressure in the chamberP builds up to a point sufiicient to overcome the bias of spring 31whereby the diaphragm moves downwardly, and contact finger 39 makes upits front point.

In like manner relay 120R. moves from its shown biased position to itsoperated position for making up its front point upon the 120 rate codebeing present. In like manner, the MIR. relay is responsive to the 180rate code, it being noted that the spring tension of the I80R relay isgreater than that of the IZUR relay and this latter, greater than the (Rrelay, due to any convenient or desired adjusting means such, forexample, as the two spacing washers 42 and 43. Thus, with relay [20Rthere is the single spacing washer 43, while with relay R there is nospacing washer. Accordingly, the spring bias on the three relaysincreases from the 151R. relay to the I80R relay. The adjusting meansshown is merely one example of what can be employed, it beingcontemplated that any other means, such as a threaded traveling nut, acam, or the like, can be employed.

The various circuits and instrumentalities employed in connection withthese three decoding pressure responsive relays can be of the typedisclosed in the W. D. I-Iailes patent, Reissue 19,599 of June 4, 1935,and accordingly, merely a brief description of the circuits is deemedsuificient for the present disclosure.

A series of repeating relays 2G, 2Y/G, ZY and 2B. is employed and eachof these relays has an energizing circuit including a back point of eachof the other three relays, in series, and, in addition, these energizingcircuits are closed, respectively, when all three of the pressureresponsive relays are picked up; when pressure responsive relay IBBR isreleased and the other two pressure responsive relays are picked up;when the pressure responsive relays IBIJR and IR are released, and thepressure responsive relay 15R is picked up; and when the three pressureresponsive relays are all reelased. For example, under the conditionsshown in Fig. 2, where no code is being received, all of the pressurerelays are in released position and the 2R relay is picked up through acircuit including contact finger 39 and back point of relay 15R, wire44, relay 2R, the three contact fingers 45, 46 and 41 and back points ofrelays ZY, 2Y/G and 2G respectively, and the wires 48, 49, 50 and 51.

The cab signal employed in this form of the invention is also of thefour aspect type and the indications are the same as described above inconnection with Fig. 1. The circuits for energizing the lamps of the cabsignal are obvious from the drawings, it being noted that the lamp R isenergized through a circuit including contact finger 52 and front pointof relay 2R. In like manner, the other lamps as G are energized throughcircuits controlled by the correspond ing contact fingers as contactfinger 53 of relay 2G.

Associated with the three relays ZY/G, ZY and 2R are three stick relay2Y/GS, ZYS and 2R8 each of which has a stick circuit including a contactfinger and front point of its corresponding control relay. The first twoof the relays have pick-up circuits including contact fingers and frontpoints of the next referred to relay in its own series. For example,relay ZY/GS has a pick-up circuit including contact finger 54 and frontpoint of relay 2Y8. Likewise, relay 2Y5 has a pick-up circuit includingcontact finger 55 and front point of relay 2R5. The pick-up circuit forrelay 2R8 passes through an acknowledging contact finger 56 of anacknowledging contactor Ack.C., whereby it is necessary to operate theacknowledging contactor in order that relay ZRS be picked up.

Employed in this system is a whistle valve WV which sounds whenenergized and silent when deenergized, and this whistle valve canreceive energy when the relay ZY/GS is in retracted position, and anyone of the three relays 2R, 2Y and 2Y/G is in attracted position or whenthe acknowledging contactor is depressed so as to make up acknowledgingcontactor finger 51 with its back point.

Under the traffic conditions illustrated in Fig. 2, relay 2R. isenergized to close its contact finger 53 on its front point but sincerelay ZY/GS is in attracted position, the whistle valve is deenergizedand hence is silent.

The circuits are so arranged that, as the code changes from more to lessrestrictive, that is, from no code up toward the 180 rate code, therelays 2Y, etc., pick up, and the relay ZY/GS remains up, since theserelays are sufficiently slow to release to bridge over momentarydeenergized periods. Thus, as the conditions on the trackway change frommore to less restrictive, the whistle valve is maintained deenergized,and hence silent.

On a change of traffic conditions to more restrictive, each changeresults in the whistle valve becoming energized and requires operationof the acknowledging contactor Ack.C. to deenergize it before it issilenced. For example, should the code in force be the 180 rate, thelamp G is lighted and the relay 2G is energized, and all of the stickrelays 2R6, etc., are deenergized so that the whistle valve circuit isclosed at contact finger 59 and back point of stick relay ZY/GS, but isopen at the three front points of the three relays 2R, ZY and 2Y/G.

Assume now that the code changes to a more restricted one such as the120 rate. In these circumstances, the pressure responsive relay |Rreleases its contact finger to thereby pick up relay ZY/G and change thesignal aspect to approach restricting by lighting the lamp Y/G Thewhistle valve is energized through a circuit including wires 60, El,contact finger 62, and front point of relay 2Y/G, wires 63, 54 and 65and contact finger 59 and back point of relay 2Y/GS.

To silence the whistle valve, the acknowledging contactor must bedepressed whereby to pick up relay 2R8 through its pick-up circuit whichincludes acknowledging contactor finger 56 and back point. With relayZRS picked up, relays 2Y3 and 2Y/GS pick up in the order named withrelay ZY/GS sticking up through its stick circuit which includes contactfinger 65 and front point, of relay ZY/G. This opens the whistle valvecircuit at contact f nger 59 and silences the whistle. The acknowledgingcontactor can now be released.

The acknowledging contactor is constructed to avoid its misuse by havingthe contactor finger 51 so arranged that, when the contactor isdepressed, the whistle valve is energized through this contact finger 51and its back point, this protective energizing circuit including wires97 and 6.8.

From the above it can be seen that, in the form of invention shown inFig. 2, and described just above, the same functions are carried out asin connection with the form of invention described in connection withFig. l. Asknowledgment is required only upon a change to morerestrictive conditions and the system depending primarily for itsfunctions on hydraulic, or other fluid means, for influencing pressureresponsive devices to decode the coded trackway control energy.

It is to be understood that this specification contemplates suchvariations and modifications as may occur desirable or practical fromtime to time without departing from the spirit of the inventiondisclosed herein.

The above rather specific description of two forms of the presentinvention has been given solely by way of example, and is not intendedin any manner whatsoever in a limiting sense. All such variations andmodifications as may be made from time to time are intended to becovered by this application insofar as they are not specificallyexcluded therefrom by a reasonable interpretation of the scope of theappended claims.

Having described my invention, I new claim:

1. In a train control system for railways, in combination with means forplacing, on a trackway, control energy variously coded in accordancewith trafiic conditions ahead, a receiver positioned to receive thecontrol energy, pressure producing means, an operative connectionbetween the receiver and the pressure producing means to control thelatter to produce various pressures in accordance with the respectiveenergizations of the receiver, a plural aspect signal, circuit means forcontrolling the signal, and means in the circuit means respectivelycontrolled by said various pressures produced by the pressure producingmeans, for caus ng the signal to display various signal aspects.

2. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections, means for placingcoded control energy. coded variously in accordance with trafficconditions ahead, on the trackway, a receiver positioned to be energizedby the control energy, a plural aspect signal, circuit means fordistinctively controlling the signal, a pressure producing deviceoperatively connected to the receiver for producing various pressures inaccordance with the respective codes energizing the receiver, andcontacts in the circuit means respectively controlled by said variouspressures, for causing the signal to display various signal aspects,

3, In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections. means for placingcoded control energy, coded variously in accordance with trafficconditions ahead, on the means comprising,

trackway, a receiver positioned to be energized by the control energy, aplural aspect signal, circuit means for distinctively controlling thesignal, pressure producing means operatively connected to the receiverfor producing various pressures in accordance with the respective codesenergizing the receiver, the pressure producing a pump, an atmosphericchamber open to atmosphere, a pressure chamber, means interconnectingthe two chambers, a connection from the atmospheric chamber to the pumpinput, and a connection from the pump output to the pressure chamber,and contacts in the circuit means respectively controlled by saidvarious pressures in said pressure producing means for causing thesignal to display various signal aspects.

4. In train control systems for railways, in combination, a streach oftrack divided into electrically isolated sections, means for placingcontrol energy, coded variously in accordance with traffic conditionsahead, on the trackway, a receiver positioned to be energized by thecontrol energy, a plural aspect signal, circuit means for distinctivelycontrolling the signal, a pressure producing device operativelyconnected to the receiver for producing various pressures in accordancewith the respective codes energizing the receiver, the pressureproducing device comprising, a pump, an atmospheric chamber open toatmosphere, a pressure chamber, means interconnecting the two chambers,a connection from the atmospheric chamber to the pump input, and aconnection from the pump output to the pressure chamber, a U tubecommunicating at one side with the pressure chamber and at the otherside with atmosphere, electrically conducting fluid in the tube, andcontacts positioned in the tube at various levels and included in saidcircuit means and efiective, respectively in accordance with saidvarious pressures, for causing the signal to display various signalaspects.

5. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections, means for placingcoded control energy coded variously in accordance with trafficconditions ahead on the trackway, a receiver positioned to be energizedby the control energy, a signal having plural aspect signal means todisplay a plurality of aspects, circuit means for distinctivelycontrolling the signal, a pressure producing device operativelyconnected to the receiver for producing various pressures in accordancewith the respective codes energizing the receiver, contacts in thecircuit means made variously effective, respectively, in accordance withthe various pressures in said device, for causing the signal to displayvarious signal aspects, the pressure producing device comprising, apump, an atmospheric chamber open to atmosphere, a pressure chamber,means interconnecting the two chambers, a connection from theatmospheric chamber to the pump input, and a connection from the pumpoutput to the pressure chamber, two U tubes, each with one leg open toatmosphere and the other leg connected to the pressure chamber. saidcontacts including a pair of contacts for each signal aspect means withone of each pair in the atmosphere leg of one tube and the other in thepressure leg of the other tube, and electrically conducting fluid in thetwo tubes.

6. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections,,means for placingcontrol energy, coded variously in accordance with trafic conditionsahead, on the trackway, a receiver positioned to be energized by thecontrol energy, a signal having plural aspect signal means to display aplurality of aspects, circuit means for distinctively controlling thesignal, a pressure producing device operatively connected to thereceiver for producing various pressures in accordance with therespective code energizing the receiver, contacts in the circuit meansoperated respectively in accordance with the various pressures in saiddevice for causing the signal to display various aspects, the pressureproducing device comprising, a pump, an atmospheric chamber open toatmosphere, a pressure chamber, means interconnecting the two chambers,a connection from the atmospheric chamber to the pump input, and aconnection from the pump output to the pressure chamber, two U tubes,each with one leg open to atmosphere and the other leg connected to thepressure chamber, said contacts including a pair of contacts for eachsignal aspect means with one of each pair in the atmosphere leg of ontube, and the other of each pair in the pressure leg of the other tube,and electrically conducting fluid in the two tubes, the two contacts ofeach pair in the two tubes being arranged in reverse order, inelevation, in the two tubes and the two contacts of each pair for eachsignal aspect means being connected in series with each other and withits signal aspect means.

7. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections, means for placingcontrol energy, coded variously in accordance with trafiic conditionsahead, on the trackway, a receiver positioned to be energized by thecontrol energy, a signal having plural aspect signal means fordisplaying a plurality of signal aspects, varying in restrictiveness,circuit means for distinctively controlling the signal, a pressureproducing device operatively connected to the receiver for producingvarious pressures in accordance with the respective codes energizing thereceiver, contacts in the circuit means operated, respectively, inaccordance with the various pressures for causing the signal to displayvarious signal aspects, the pressure producing device comprising, apump, an atmospheric chamber open to atmosphere, a pressure chamber,means interconnecting the two chambers, a connection from theatmospheric chamber to the pump input, and a connection from the pumpoutput to the pressure chamber, two U tubes each with one leg open toatmosphere and the other leg connected to the pressure chamber, saidcontacts including a pair of contacts for each signal aspect means withone contact of each pair in the atmosphere leg of one tube and the otherof each pair in the pressure leg of the other tube, electricallyconducting fluid in the two tubes, a normally inactive penalty means,manually operative acknowledging means, and pressure controlled meansconnected to the pressure chamber and operative to make the penaltymeans active, upon a change in signal aspect to a more restrictiveaspect, until after operation of the acknowledging means.

8. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections, means for placingcontrol energy, coded variously in accordance with traffic conditionsahead, on the trackway, a receiver positioned to be energized by thecontrol energy, a signal having plural aspect signal means fordisplaying a plurality of signal aspects varying in restrictiveness,circuit means for distinctively controlling the signal, a pressureproducing device operatively connected to the receiver for producingvarious pressures in accordance with the respective codes energizing thereceiver, contacts in the circuit means operated respectively inaccordance with the various pressures in said device for causing thesignal to display various aspects, the pressure producing devicecomprising, a pump, an atmospheric chamber open to atmosphere, apressure chamber, means interconnecting the two chambers, a connectionfrom the atmospheric chamber to the pump input, and a connection fromthe pump output to the pressure chamber, two U tubes, each with one legopen to atmosphere and the other leg connected to the pressure chamber,said contacts including a pair of contacts for each signal aspect meanswith one contact of each pair in the atmosphere leg of one tube and theother in the pressure leg of the other tube, electrically conductingfluid in the two tubes, the corresponding contacts in the two tubesbeing arranged in reverse order as to their elevation in the two tubes,the two contacts for each signal aspect means being in series with eachother and the signal aspect means, a normally inactive penalty means,manually operative acknowledging means, and pressure controlled meansconnected to the pressure chamber and operative to make the penaltymeans active upon a change in signal aspect to a more restrictive one,until after operation of the acknowledging means.

9. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections, means for placingcontrol energy, coded variously in accordance with trafiic conditionsahead, on the trackway, a receiver positioned to be energized by thecontrol energy, a plural aspect signal, circuit means for distinctivelycontrolling the signal, a pressure producing device operativelyconnected to the receiver for producing pressures varying in accordancewith th particular code energizing the receiver, a plurality of contactsin the circuit means, elastic means biasing the contacts to differingdegrees, a pressure responsive means operatively connected to eachcontact, and means communicating each pressure responsive means with thepressure in the pressure producing device.

10. In train control systems for railways, in combination, a stretch oftrack divided into electrically isolated sections, means for placingcontrol energy, coded variously in accordance with traflic conditionsahead, on the trackway, a receiver positioned to be energized by thecontrol energy, a plural aspect signal, circuit means for distinctivelycontrolling the signal, a pressure producing device operativelyconnected to the receiver for producing pressures varying in accordancewith the code energizing the receiver, a plurality of contacts in thecircuit means, spring means biasing each of the contacts to difieringdegrees, a diaphragm operatively connected to each contact, and meanssubjecting each diaphragm to the pressure in the pressure producingdevice for distinctively controlling the signal.

CHARLES S. BUSHNELL.

